FS-independent bash backup

Dirty and quick, a little script to backup an entire hard drive from bash:

# License: do what you want but cite my blog ;)
# http://binaryunit.blogspot.com
# *** superSalva 1.0 by Eugenio Rustico ***
# Backup utility for ALL types of partitions
# - Easy disk/partition image *even of unknown filesystems*
# - On the fly compression: no need for temporary files
# - Customizeable process
# - May be more speedy
# - No fs-specific support
# - Reads and compress even zero-zones
# - Support for decompressor without zcat equivalent
# - Support for creating (better if bootable) iso images
# - Support for md5sum integrity verification (!)
# - Free space checking
# - Wizard
# - Final statistics and estimated time
# - Trap for CTRL+C

# Device to be backupped, even if NTFS or unknown. May be a partition or a whole disk
export DEVICE=/dev/hda6

# AUTOMATIC: device capability, in kb
export DEVICE_DIM=`df -k | grep $DEVICE | awk {'print $2'}`

# Actually unused
export DEVICE_FREE=`df -k | grep $DEVICE | awk {'print $4'}`

# Destination/source directory. If destination, should have $(dim of $DEVICE) space free
# Do NOT locate destination on the same drive you're backupping!
# export DIR=/d/ripristino/e
export DIR=/pozzo

# Destination/source base filename. During backup files are overwritten.
export FILENAME=Immagine_E_20_6_2006

# On the fly compression commands. Shoud support reading from stdin and writing on stdout
# DEFAULT: gzip, well-known
# EXPERIMENTAL: 7zip, slower but better compression. YOU MUST HAVE 7zip ALREADY INSTALLED. But does "7cat" exist?
export COMPRESSOR=gzip
export DECOMPRESSOR=zcat

# Compression parameters
# Actually, only a compression level sent to gzip

# Compressed file extension. Optional but useful
export EXTENSION=gz

# Number of piecese to skip while backuppin/restoring
# Useful for testing and for resuming interrupted backups
# Default: 0
export SKIP=0

# Block size. NOTE: from it depend default piece dimensions!
export BLOCK_SIZE=1024

# Dimension of pieces to compress and backup, in kb.
# Too small = too many pieces, not useful
# Too large = unefficient compression
# MAX = 4194303 (if dest fs is not FAT, may be higher), few pieces
# 524288 (512 Mb)
# 262144 (256Mb)
# 131072 (128 Mb), many pieces
# 65536 (64 Mb)
# 32768 (32 Mb), definitely too much pieces!
# MIN = 1 (nonsense)
# DEFAULT = 1048576 (1 Gb, RECOMMENDED)
# NOTE: this values are block-size dependent (in this case, we use 1024 bytes blocks)
export PIECE_DIM=32768

# AUTOMATIC: number of pieces
# Should be plus one, but it's zero based so no matter


# Want to see what I'm doing?
export VERBOSE=1

echo " *** superSalva 1.0 *** "
echo "Device: $DEVICE ($DEVICE_DIM kb)"
echo Compressor: $COMPRESSOR
echo Decompressor: $DECOMPRESSOR
echo Parameters: $COMPRESSOR_PARAMS
echo Device: $DEVICE
echo Pieces: $(($NUM+1)) pieces, $PIECE_DIM kb each
echo Action: $ACTION
echo Ready? CTRL+C to abort, ENTER to start. May take LONG time.

export SUM=0
for i in `seq $SKIP $NUM`
export FILEN="$DIR/$FILENAME.$(($i+1)).$(($NUM+1)).$EXTENSION"
export SK=$(($i*$PIECE_DIM))
#if [ ]
if [ "$ACTION" == "RESTORE" ]
echo "* Decompressing and writing piece $(($i+1)) of $(($NUM+1)) (kb $(($SK+1)) to $((($i+1)*$PIECE_DIM)))..."
if [ $VERBOSE == 1 ]; then echo $COMMAND; fi
echo "* Successfully restored $FILEN"
echo "* Reading and compressing piece $(($i+1)) of $(($NUM+1)) (kb $(($SK+1)) to $((($i+1)*$PIECE_DIM)))..."
if [ $VERBOSE == 1 ]; then echo $COMMAND; fi
export LAST_DIM=$((`ls -l $FILEN | awk {'print $5'}`/1000))
echo "* Saved $FILEN ($LAST_DIM kb, ratio $(((100*$LAST_DIM)/$PIECE_DIM))%)"
export SUM=$(($SUM+$LAST_DIM))

if [ $ACTION == "RESTORE" ]
echo "Finished. $DEVICE seems to be restored."
echo "Finished. $(($NUM+1)) files, tot $SUM kb ($((100*$SUM/$DEVICE_DIM))% of original $DEVICE size)"
echo Bye!

Thanks to dd. Features:
  • On the fly compression
  • Non need for temporary files
  • File-system independent
  • Backup and restore facilities
  • Keeps master boot records
  • ...
TODO: lots of things (checksumming facilities, configuring wizard, free space checking, command tests...); the complete TODO list is inside the script.

Call for developers: stop designing for IE!

There's one big truth you learn if you have a little experience in web designing and/or developing: you have to get stuck with Internet Explorer bugs.

The work of web developers is nowadays made of two parts:

  1. Write the website and test it (usually one test is enough for Firefox 1, Firefox 2, Opera, Safari, Camino, Konqueror, etc. on any platform)
  2. Rewrite the CSS and test it again with Internet Explorer 6 and 7
Internet Explorer (any version) is not standard compliant. Yes, we're talking about W3C standards, the ones made with efforts by the members of this worldwide consortium aiming to give a bit of order to the chaos of internet technologies and to improve websites usability. Ironically, Microsoft is a W3C member despite its known attitude not to comply with many international standards.

Now, what's the problem? Simply, because of Microsoft whims in fact of standards (especially for CSS) most web developers have to do the double work. Personally, I'm tired of wasting time (and money) to double-debug my works. And because so many people use (mainly not intentionally) Internet Explorer, noone would pay for a website not viewable with IE.

A solution? If you can decide about your website (read: if it's not committed, or you can talk about it with your boss) do the right thing: do not test and redesign your CSS for IE. Just leave a warning like this one:

Warning: due to a bug in Internet Explorer, this website may look like ugly. To view this page correctly, please use a standard compliant browser. Thanks.

This may seem rough, but it's a bit ironic to smart readers and, above all, it's perfect if you're tired or wasting your worktime for IE. Adding a sponsored link to Firefox (one like "Get Firefox for better browsing", you know what I'm talking about) below the warning makes it even more useful.

Please note that this way you won't loose all your IE users: they should just see the website ugly, as IE naturally renders it, and they should be informed about the cause of that (while being anyway able to use it). Moreover, if they'll start using Firefox (or Opera, or...) they'll experience a better browsing experience (especially people who still use primitive non-tabbed broswers like IE6). And they'll be thankful to you.

Web developers (and their bosses) should keep in mind that if a standard compliant website is not correctly displayed on IE this is not a problem of the website itself: this is a problem of IE. And the users, both geek and inexperienced ones, have the right to know that someone gave them a buggy browser. Hiding this, by building a separate style just for IE, will feed users' ignorance, keeping web development tedious and time wasting.

A live example of this philosophy is Hash'em all!, one of my last works: IE is the only browser in which the central DIVs are not correctly sized and cover all the window from left to right. I'll add some screenshots asap.

You probably don't need a proof that IE brings so many problems for developers, but in case you do here are some references:
Similar initiatives:
UPDATE: I added to Hash'em all! the link to a campaign called "Ugly on IE, not for my fault". If you wish to do the same don't hesitate to add the same image (or another better) linking to this post.

Hash'em all: free online text and file hashing

I couldn't find an online hashing service which allowed to hash text strings and files using several different algorithms (MD5, SHA1, SHA512, RIPMED, Whirlpool, HAVAL, etc.); so, I made one. And after hours and hours of creative efforts, here's the name I conceived: Hash'em all!.

Layout is really simple but (big surprise!) there's a rendering problem with Internet Explorer (any verision). The central DIVs are correctly sized in Firefox, Opera, Safari, Konqueror, Camino and every other standard-compliant web-browser; unfortunately, IE is not in this list (while MS is part of W3C consortium... bah!).

I will *never* redisign the site to fit IE bugs with a CSS selector and a separate stylesheet: I have no intention to do again the work because of Microsoft's whims.
Using IE Hash'em all! is still usable, but ugly. If you want a nice interface, please use a W3C-compliant browser. And, if you'd like to know what's the problem: it seems that in IE there's no way to have a centered auto-adaping DIV, because IE totally ignores display: table; CSS attribute.

Features in brief:

  • It's free
  • It's fast (less than 0.1 second for most queries)
  • There's no limit on the number of queries
  • It allows to hash files up to 10Mb
  • You can choose up to 35 different digests
  • Allows empty strings
  • It's cute (but that's subjective...)
Yes, there are just a few google ads. But it's free (as in free beer, for now) ;]

Workaround: dpkg goes Segmentation Fault

So, your apt-get [dist-]upgrade stops when a post/pre-installation script goes in Segmentation Fault. The strange thing is that the same script, extracted from your favourite deb package, works if launched standalone. That's probably a debconf or dpkg bug but, frankly, I didn't even google to find if it's really a known bug: I get this problem quite often on my Debian testing (especially while upgrading libc6, tzdatam console_common), so I chose to spend my time looking for a workaround. And, finally, I found a very simple one.

That's, more or less, the error I get (note: my system is localized in italian):

(Lettura del database ... 184524 file e directory attualmente installati.)
Mi preparo a sostituire libc6 2.7-3 (con libc6 2.7-5) ...
Spacchetto il sostituto di libc6 ...
Configuro libc6 (2.7-5) ...
dpkg: errore processando libc6 (--install):
il sottoprocesso post-installation script è stato terminato dal segnale (Segmentation fault)
Sono occorsi degli errori processando:

In a nutshell, my solution is:
  • Unpack the .deb package causing the problem and grab the meta-files
  • Clear the pre/post-installation script (depending on which one causes the segmentation fault)
  • Pack a new .deb package with these fake scripts and install it
  • Run manually the scripts you modified (do this before the installation if it was a preinst or pre/post-rm)
  • Done: you can go on with your dist-upgrade
That's easy to do within a bash shell if you know the right commands. And they are:

# Make a copy of crashing package
cp /var/cache/apt/archives/crashing_pkg_x.y.z.deb ./crashing_package.deb

# Extracts package data
dpkg-deb -x crashing_package.deb ./temp_dir

# Extracts package meta-files
dpkg-deb -e crashing_package.deb ./temp_dir/DEBIAN

# Make fake post/pre installation scripts
echo "echo Fake" > ./temp_dir/DEBIAN/postinst

# Pack a new modified package
dpkg-deb -b ./temp_dir/ mod_package.deb

# Install the hacked package (should not go in segfault)
dpkg -i mod_package.deb

# Manually run postinst script

# Clean
rm -rf ./temp_dir
rm crashing_package.deb mod_package.deb
Dirty and functional, as usual. But pay attention to the manual execution of scripts: they may crash, or refuse to go on, or they may contain debconf commands that bash can't execute; so my advice is: take a look inside and try to manually do, step by step, what the script was supposed to do (uninstalling packages, stopping processes, restarting daemons, upgrading configurations, and so on).

I guess you're experienced enough to change them to suit your needs (and, above all, I'm in a hurry now!). So, good luck and may the GNU-force be with you =)